Several years ago when PCI-Express was being developed, the
technology was also being designed to support devices outside of the
traditional computer enclosure. While "internal" PCI-Express took
off, development and support for external devices was slow. This week, the PCI
Special Interests Group (PCI-SIG) announced the availability
of the PCI-Express external cable specification revision 1.0.
With the new specifications fully defined, cables will be developed for all
PCI-Express link widths including: x1, x4, x8 and x16. This allows for devices
such as external high-speed storage controllers, network or fabric interfaces
and graphics adapters to use the technology.
According to PCI-SIG chairman Al Yanes, external PCI-Express
products should now be in full development and show up on the market in less
than a year. "This specification helps the industry create new products that
will take PCIe technology out of the box – enabling PCIe solutions for IO
expansion drawers, external graphics processors, tethered mobile docking,
communications equipment and embedded applications,” said Yanes.
External PCI-Express devices will be able to use signaling rates up to 2.5
gigatransfers per second (GT/sec). Of course, the host, adapter and cable must
be able to support those speeds, but the future looks promising according to
the specification's outline. Later on, 5GT/sec. rates will be possible. Some
applications for this type of technology include stacking storage arrays
together by using the external PCI-Express interconnect rather than relying on